The present invention relates to a balancing piece for ventilated-disc brakes, which is fixedly received within a cooling vent formed in a ventilated disc so as to improve rotational balance of the disc.
In general, a ventilated brake disc presently in wide use includes in a radially outward portion thereof a number of cooling vents which are disposed in the almost radial direction between the two rubbing or friction surfaces. As the disc is rotated, air is caused to flows through the vents thereby increasing heat radiating capability of the disc. Ventilated discs of such type, however, tend to lose their rotational or dynamic balance because of the provision of the multitude of cooling vents. In view of the need to improve the dynamic balance, such type of ventilated discs have conventionally employed a balancing piece which is fixedly positioned within the vent.
Among the presently available balancing pieces for use on those ventilated discs, the one disclosed in the Japanese "Jitsukousho," No. 53-33104 has been found highly excellent in terms of ease of installation thereof within the vent and locking ability to restrain itself from moving out of engagement with the vent. This balancing piece includes a wide portion which snugly fits a radially outward portion of a vent with the edges thereof being in contact with diagonally opposed corners of the vent. The balancing piece also includes a head portion which, during installation of the balancing piece, is projected through an open end of the vent on the disc center side and twisted to put its tapered edges into engagement with edges of internal wall surfaces at the above inner open end of the vent, thereby preventing the balancing piece from moving out of position toward the outer edge of the disc. Additionally, since the radially disposed vent is commonly formed so that its crosssectional area is increasing toward the outer edge of the disc, the wide portion snugly fitting the radially outward portion of the vent is restrained from moving inwardly toward the center of the disc. Thus, the balancing piece is securely fixed in position within the vent without any subsequent outward or inward movement off its fixed position.
As previously described, the balancing piece disclosed in the Japanese "Jitsukousho," No. 53-33104 would be highly praised in its excellence if its intended installation theory could be completely put to work. Actually, however, it has been conventionally found difficult to put the theory into practice. Thus, the balancing piece has offered a disadvantageous tendency of becoming loosened within the vent due to insufficient self-fastening condition and thus suffered undesired rattling noises. In concrete terms, the wide portion which fits a tapered opening of the vent, is liable to shift outwardly out of position toward the outer edge of the disc when the head portion is twisted into engagement with the inner open end of the vent, and as a result, there may develop a gap between the edges of the wide portion and the interior walls of the vent which may cause the rattling problem. In addition, dimensional errors of the vent may also result in a loose fit of the wide portion in the vent after the tapered edges of the head portion are put into engagement with the inner open end of the vent on the disc center side. This may compound the rattling problem of the balancing piece.